Previously, it was demonstrated that purified glutamine synthetase from E. coli undergoes oxidative inactivation by different enzymatic and nonenzymatic systems. This inactivated enzyme is more susceptible to proteolytic digestion by known proteases and protease preparations from E. coli. Studies in this laboratory demonstrated that NADH-diaphorase is the simplest enzymatic system which catalyzes oxidative inactivation of glutamine synthetase. This inactivation is qualitatively similar to inactivation catalyzed by the microsomal cytochrome P450 system, Pseudomonas putida mixed function oxidase system and ascorbate system. Studies have been undertaken to test the capacity of NADH-diaphorase to inactivate enzymes other than glutamine synthetase in order to test the generality of this phenomenon. Techniques used in these studies have included polyacrylamide gel electrophoresis, chromatographic techniques, enzymatic assay of functional proteins, and high pressure liquid chromatography.